My earlier U.S. Pat. Nos. 4,205,740, 4,040,876 and 4,304,521 disclose pulsating gravity-type conveyors which are particularly desirable for conveying palletized loads, specifically articles supported on conventional wooden pallets, and which are also highly desirable for use in storage-rack systems for permitting "first in-first out" storage of palletized loads. In this known conveyor or storage rack system, the loaded pallets are supported directly on the conveyor rollers, and the conveyor itself involves a large number of rollers which are disposed in longitudinally adjacent relationship and are supported by a carriage or rail structure which enables the rollers to vertically reciprocate in a cyclic or repetitive manner. This arrangement physically causes the palletized loads to be intermittently lifted and lowered relative to a longitudinally extending stationary brake, the pallets hence being stopped by the brake when the pallets and rollers are in their lowered positions. While this known arrangement has proven highly successful and desirable for transporting and storing palletized loads, particularly in storage racks, nevertheless this system has been recognized to possess features which are, in some instances, considered less than optimum. For example, this arrangement requires a large number of rollers disposed longitudinally in series and extending along the length of the conveyor, with the rollers themselves being mounted on carriages or rails which can be vertically reciprocated. This hence increases the expense and complexity of the overall system. In addition, this known arrangement normally requires that the conveyor be provided with a substantial pitch, such as six inches of pitch or vertical drop for each ten feet of length in order to ensure that the palletized loads will freely move by gravity downwardly along the irregular support surface defined by the pulsating rollers. The magnitude of pitch becomes significant when the conveyor or storage rack is of substantial length, and hence can restrict the number of conveyors which can be vertically stacked directly above one another within the rack.
In recent years, it has been proposed to utilize wheeled pallets or buggies for supporting, storing and transporting goods or articles, and some of the known systems have relied upon a gravity-type conveying arrangement for controlling these wheeled buggies. These known arrangements, while they are desirable in that they require wheels only on the pallets and hence permit the pallets to be rollingly supported on flat support surfaces, have nevertheless met with only limited commercial success in view of the great difficulty experienced in controlling the gravity-urged movement of the buggies downwardly along an incline. For this reason, gravity-type buggy conveying arrangements have not met with wide commercial success and, in fact, have had only minimal commercial utilization.
Hence, it is an object of this invention to provide a transporting or conveying arrangement, specifically suited for use in a storage rack, which arrangement employs gravity-urged wheel-supported buggies or pallets for storing and transporting goods thereon. In the arrangement of this invention, the pallets or buggies can be rollingly supported on elongated rails having flat support surfaces for engagement with the buggy wheels, and a pulsating or cyclic activating means coacts with and extends longitudinally along the apparatus for causing the buggy to be cyclically relatively moved into and out of engagement with a longitudinally elongated brake in a repetitive manner to permit the buggy to move by gravity in a controlled steplike manner downwardly along the inclined support rails. In this manner, a controlled and failsafe operation is achieved so as to regulate the gravity-urged movement of the buggies and of the loads thereon, and at the same time the control can be readily achieved by a pulsating activating means which extends longitudinally along the apparatus to provide the desired intermittent frictional engagement between the pallet and the brake.
In a preferred embodiment of the invention, the brake is mounted on and extends longitudinally of the framework and cooperates with brake pads secured to the underside of the buggy. A separate pulsating or cyclic activating device coacts with one of the support rails to periodically and cyclically lift and lower the one support rail a small extent so that the buggy hence intermittently disengages and then engages, in a repetitive fashion, the brake pad to cause a steplike gravity-urged movement of the buggy downwardly along the support rails.
In the preferred embodiment, the brake pad on the buggy and the brake member on the frame are preferably provided as opposed channellike elements which nest one within the other, these elements having diverging sidewalls which function as guides to facilitate automatic realigning or recentering of the buggy when the latter is lowered into engagement with the brake member.
With the improved arrangement of this invention, the buggies can be successfully gravity-urged downwardly along the rails while providing the rails with only minimum pitch, such as a pitch in the order of two to four inches per each ten feet of horizontal length. This minimizes the overall vertical drop as the arrangement extends over a substantial horizontal length, and hence permits a storage rack in some instances to accommodate a greater number of vertically stacked bays within the same maximum rack height.
With the improved arrangement, there is provided a plurality of buggies which in effect comprise slave pallets, which slave pallets comprise an integral part of the system and mount the rollers thereon. These slave pallets themselves define an upper support surface which permits loads to be positioned thereon, which loads normally comprise wooden pallets having goods or articles thereon. The use of these slave pallets as buggies hence provides the system with a high degree of reliability and dimensional stability so as to provide precise control over the gravity-urged movement.
Other objects and purposes of the invention will be apparent to persons familiar with systems of this general type upon reading the following specification and inspecting the accompanying drawings.